Field of the Invention
The present invention relates to a photoacoustic apparatus which acquires optical property information by using a photoacoustic wave, an operation method of the photoacoustic apparatus, and a program.
Description of the Related Art
A study of an optical imaging apparatus to image information inside a subject, which information is acquired by emitting light from a light source such as a laser to the subject such as a living body and acquired based on the incident light, has been actively done in a medical field. As one kind of the optical imaging technique, there is photoacoustic imaging (PAI). In the photoacoustic imaging, pulsed light generated in a light source is emitted to a subject and an acoustic wave (typically, ultrasonic wave) generated in a subject tissue which absorbs energy of the pulsed light propagated and diffused in the subject is received. Based on the received signal, imaging of information of the subject is reconstructed.
That is, by using a difference between absorptance of optical energy in an object region such as a tumor and that in other tissues, an elastic wave (photoacoustic wave) generated when a region to be inspected absorbs the emitted optical energy and instantaneously expands is received by a probe. By performing mathematical analysis processing on this received signal, optical property distribution inside the subject, specifically, initial sound pressure distribution, optical energy absorption density distribution, absorption coefficient distribution, or the like can be acquired.
These pieces of information can also be used, for example, for a quantitative measurement of a specific substance inside the subject such as oxygen saturation in blood. Recently, by using the photoacoustic imaging, a preclinical study to image a blood vessel image of a small animal or a clinical study to apply this principle to a diagnosis of a breast cancer or the like has been actively done (“Photoacoustic Tomography: In Vivo Imaging From Organelles to Organs”, Lihong V. Wang Song Hu, Science 335, 1458 (2012)). In the photoacoustic imaging, generally, it is desired to image optical property distribution of an optical absorber inside the subject.